# #单分支if语句
# #函数的功能：将字符串str当成有效的表达式来求值并返回计算结果。
# score = eval(input('请输入成绩分数'))
# if score >=60:
#     print("成绩已及格")

#if语句嵌套使用
# score = eval(input("请输入成绩分数"))
# if 60 <= score:
#     print("成绩已及格")
#     if 90 <= score <= 100:
#         print("成绩很好")

# 双分支if-else
# a = 89
# if a > 20:
#     print("变量a大于20")
# else:
#     print("变量a不大于20")

#if语句中嵌套if-else
# score = eval(input("请输入成绩分数:"))
# if score >= 60:
#     print("成绩及格")
#     if score >= 90:
#         print("成绩很好")
#     else:
#         print("成绩一般")

#if-else语句中嵌套if-else
# score = eval(input("请输入成绩分数:"))
# if score >= 60:
#     print("成绩及格")
#     if score >= 90:
#         print("成绩很好")
#     else:
#         print("成绩一般")
# else:
#     print("成绩不及格")
#     if score < 30:
#         print("成绩极差")
#     else:
#         print("成绩较差")

#多分支结构：if-elif-else
# score = eval(input("请输入一个成绩分数"))
# if score >= 90:
#     print("成绩优秀")
# elif score >= 80:
#     print("成绩良好")
# elif score >= 70:
#     print("成绩中等")
# elif score >= 60:
#     print("成绩较好")
# else:
#     print("成绩不及格")
#
# #练习
# a = eval(input("输入一个年份"))
# if a/4==0 and a/100=1 and a/400=1:
#     print("是润年")
# else
#     print("不是闰年")

# 条件循环：while
# a = 1
# while a <= 100:
#     print('今天是第%d天'% a)
#     a = a + 1

# n = 1
# s = 0
# while n <= 1000:
#     s = s + n
#     n = n + 1
#     # print(s)
# print(s)

#遍历循环：for
# for i in [1,2,3,4]:
#     print(i)

# for i in range(1,11):
#     print(i, end=' ')
#     print()   #换行符
# for i in range(1, 11, 2):  #前闭后开
#     print(i,end=' ')
#     print()
# for i in range(2, 11, 2):
#     print(i,end=' ')
#while中嵌入while
# i = 1
# while i <= 5:
#     print("上班星期为:",i)
#     i = i+1
#     t = 9
#     while t <= 17:
#         print("时间段:",t,end=' ')
#         t = t+1
#     print()

#for中嵌入for
# i = 1
# for i in range(1, 6):
#     print('上班为周：', i)
#     for t in range(9, 18):
#         print('时间段为：', t, end=' ')
#     print()

# #while嵌入while实现九九乘法表
# i = 1
# while i <10:
#     j = 1
#     while j <= i:
#         print("%d*%d=%d"%(j,i,j*i,),end=' ')
#         j+=1
#     print()
#     i += 1
#
# for i in range(1, 10):
#     for t in range(1,i+1):
#         print("%d*%d=%d"%(t,i,t*i),end='')
#     print()

#while中使用break跳出循环
# i = 0
# while i <= 5:
#     i += 1
#     print('星期为：', i)
#     if i == 3:
#         break
#
# i = 1
# while i <= 5:
#     if i == 3:
#         break
#     print('星期为：', i)
#     i += 1

#for循环中使用break语句
# for i in range(1, 6):
#     print('星期为：', i)
#     if i == 3:
#         break
#
# for i in range(1, 6):
#     if i == 3:
#         break
#     print('星期为：', i)

# # while循环中使用continue语句
# i = 0
# while i < 5:
#     i = i + 1
#     if i == 4:
#         continue
#     print('星期为：', i)
#
# #for循环中使用continue语句
# for i in range(1, 6):
#     if i == 4:
#         continue
#     print('星期为：', i)